The present invention relates to an improved depth gauge to be used with a cutter.
Cutters for cutting devices movable along a path for cutting a kerf in a workpiece, such as may be found in a saw chain or saw blades for cutting wood, often have a cutter portion with a leading cutting edge and a depth gauge portion spaced forwardly of the cutting edge to control the depth of cut taken by the cutter. In powered devices the depth gauge is instrumental in reducing the possibility of kick-back during operation of the saw on which the cutter runs.
Depth gauges in the past generally have included a single thickness of cutter material which extends upwardly in a region spaced forwardly from the cutter edge as disclosed in Silvon, U.S. Pat. No. 4,353,277. These prior devices generally have presented to the kerf little more width than the thickness of the plate material from which the cutter or depth gauge is formed.
Other prior devices have included cantilever-style bent-over depth gauge portions such as disclosed in U.S. Pat. Nos. 5,085,113 and 4,989,489 to Pinney, U.S. Pat. No. 4,911,050 to Nitschmann and U.S. Pat. No. 4,841,825 to Martin.
A single thickness upright depth gauge as illustrated in 4,353,277 may have a tendency to dig into the workpiece and not provide consistent cutting depth control. Bent-over depth gauges in the past often have had weaknesses at the bend and had a tendency to break in operation. Although prior bent-over depth gauge devices provide depth of cut control, they can produce excessive friction and drag and also inhibit the free flow of chips produced by the cutters. Explaining further, if chips produced by the cutter are not allowed to flow easily under the top plate of the cutter, they will continue to build up in the kerf, and the depth gauge and cutter will tend to ride thereover producing inefficient cutting.
An object of the present invention is to provide a novel depth gauge for a cutter which overcomes the disadvantages of prior devices in an efficient and cost-effective manner.
In one embodiment of the invention, the depth gauge extends upwardly from a substantially planar body portion and when viewed from the side has an upwardly rounded forward-facing surface. However, as viewed from above, it has a rippled, or laterally deformed configuration. The lateral deformation is such as to extend to opposite sides of the main body of the depth gauge, such that when viewed from the front, it has an apparent overall width, as seen by the workpiece, which is considerably wider than the material from which the depth gauge is manufactured.
Further, the laterally deformed, or rippled, depth gauge has all portions thereof extending substantially upwardly from the main body of the depth gauge. Thus it has no bent-over, cantilevered portions which in prior devices have produced weaknesses having a tendency to break. Instead, it's laterally deformed curvilinear configuration adds strength to the depth gauge.
The depth gauge of the present invention is simple to produce, since it can be blanked from plate material to define a selected initial outline, and then deformed laterally to the offset configuration desired to provide a forward ramping configuration which produces advantageous depth gauge control characteristics for a cutter with which it is used. An added advantage of this is that an upwardly curved top surface contour is provided producing more efficient operation for the depth gauge, as opposed to previously used bent-over cantilever depth gauges which generally have substantially flat upper surfaces.
Another advantage of the present invention over previous bent-over depth gauges comes in the filing of the depth gauge to have a proper height relative to a following cutter to maintain desired depth gauge setting. With an upwardly extending, non bent-over configuration as provided by the present invention, filing to maintain desired depth gauge setting should result in no reduction in strength of the part. Conversely, in a bent-over depth gauge such filing may reduce the cross sectional thickness of the material of the depth gauge substantially weakening it.
In one embodiment of the present invention, the depth gauge extends upwardly from a body portion with a forward region, as viewed from above, being disposed at a first angle greater than 2.degree. relative to the plane of its underlying body portion and a second section positioned rearwardly of the first section which, as viewed from above, is disposed at a second angle, also greater than 2.degree. relative to the plane.
In a preferred embodiment on progressing rearwardly in the device the first section diverges at the first angle from the body plane and the second section joins the first section at a juncture section at the rear end of the first section, and then the second section on progressing rearwardly converges toward the body plane. The juncture section may define the greatest distance to which the depth gauge extends to one side of the plane, and the second section may extend across the plane, terminating at the opposite side thereof from the juncture section.
In various embodiments, the first and second sections of the depth gauge may be bent relative to each other about a line that extends upwardly from the body or may be substantially conoid having a central axis which extends upwardly from the body.
In a cutter employing such a depth gauge, a following cutting portion may be spaced rearwardly of the depth gauge, with a forwardly facing cutting edge extending transversely of the cutter at a selected elevation slightly above the highest portion of the depth gauge and with a side cutting edge spaced laterally outwardly of a laterally outward extremity of the deformed depth gauge. The configuration of the depth gauge described herein, may be produced such that the highest portion of the depth gauge is disposed substantially centrally of the side-to-side dimension of the transversely extending cutter edge.
Another advantage of the present invention is that the open space provided between the angularly disposed first and second sections of the depth gauge is able to efficiently gather and carry chips from the kerf. Raised or indented lines or other formations may be formed on the inner surfaces of the first or second sections to assist in carrying chips out of the kerf.
It has been observed that there is a substantially direct correlation between the amount of top surface area which the depth gauge presents to the workpiece and the kick-back protection provided. The present invention provides a substantial increase in top surface area over previously known upstanding depth gauges, and thus produces the added advantage of reduced kick-back potential.
In summary, the invention provides a depth gauge for a cutter having laterally deformed depth gauge sections which provide a top surface which sweeps a far wider area of the kerf than the thickness of the material from which the part is made when moving through the cut. It provides a depth gauge surface which substantial apparent dynamic has width relative to the cutter during operation and increased top surface area.
These and other objects and advantages will become more fully apparent as the following description is read in conjunction with the drawings.